Babesiosis

Presentation :

• Symptoms typically begin within 1 month after tick bite and within 2 months after transfusion of infected blood products.
• Symptoms are nonspecific and include fever (89%), fatigue (82%), chills (67%), headache (47%), myalgia (43%), and cough (28%).
• Physical examination may reveal jaundice, hepatomegaly, and splenomegaly, which rarely progresses to splenic rupture.
• The hallmark of babesiosis is hemolysis, with anemia almost invariably present. Severe disease may include thrombocytopenia, elevated serum aminotransferase levels, and acute kidney injury.

Pathophysiology :

• Caused by the intraerythrocytic protozoan Babesia microti, which is spread by Ixodes scapularis (Blacklegged Deer Tick).
• Can also occur in non-endemic regions via infected blood transfusions

Diagnostic Testing:

• Visualization of B. microti, manifesting as intraerythrocytic ring forms similar to those seen in malaria OR as tetrads resembling a Maltese cross, on thin blood smears is diagnostic.
  
• With low-level parasitemia, the sensitivity of microscopy is poor. Therefore, polymerase chain reaction should be pursued if the clinical suspicion of babesiosis is high.
• Antibody testing does not differentiate acute from previous infection and is not recommended for diagnosis.

Treatment :

• The first-line treatment for babesiosis is atovaquone plus azithromycin.
• In patients intolerant of this regimen, clindamycin plus quinine is an alternative.
• Exchange transfusion may be indicated in patients with severe infection and high-grade (>10%) parasitemia.
• Immunocompromised patients require a longer treatment duration, typically 2 weeks after documented clearance of parasites on blood smear.

Prognosis:

References:

• MKSAP